A method for a reservoir to safely respond to the possible maximum flood through optimized scheduling

Abstract

The present invention discloses a method for a reservoir to safely respond to the possible maximum flood through optimized scheduling, and the steps are as follows: S1. According to the hydrological forecast and the regulations of the reservoir operation rules, determine the flood process of the possible maximum flood, that is, the flood discharge corresponding to different flood durations; S2. Clarify the opening and closing conditions of each flood discharge structure in the reservoir and the flood discharge project system, as well as the flood discharge of each flood discharge structure at different opening degrees; S3. Clarify the flood control requirements of the reservoir and the flood control protection objectives downstream, determine the boundary conditions, and establish the constraint conditions; S4. Establish a one-dimensional hydrodynamic model of the reservoir; S5. Solve the one-dimensional hydrodynamic model under unsteady flow conditions to obtain the water surface profile and the flood discharge corresponding to different combinations, and obtain the reservoir operation plan that meets the flood control objectives through comparison and selection. When dealing with the over-standard flood, the present invention can increase the flood discharge and advance the flood discharge by adjusting and optimizing the opening and closing mode of the flood discharge facilities, and obtain the emergency operation mode.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir safety dispatching and flood control, and in particular to a method for a reservoir to cope with an exceed-standard flood by reasonably releasing the flood control storage capacity. Background Art

[0002] Flood is one of the most destructive natural disasters in the world. At the same time, due to the complex mountainous terrain and geological conditions in China, flood disasters are characterized by suddenness, multiplicity and uncertainty. Especially in the context of global climate change, relevant studies have shown that with the global climate warming, the trend of extreme floods and exceed-standard floods has increased significantly. The probable maximum flood (PMF) refers to the flood formed by the combination of various most unfavorable factors, and it is also the most serious flood in the study area. This flood is formed by the combination of the worst meteorological and hydrological conditions, and it poses a great threat to the safety of reservoir dams and downstream flood control targets. Therefore, the analysis of the dispatching optimization problem of reservoirs when facing PMF floods has important theoretical significance and engineering practical application value.

[0003] When a reservoir encounters an exceed-standard flood such as PMF, since various conventional dispatching regulations of reservoirs usually take ensuring the safety of the dam body as the primary goal when considering the threat of rare floods that the reservoir may encounter at the beginning of design. When using the conventional dispatching regulations of the reservoir to release flood for PMF, it may cause the downstream river channel to face the risk of flood disasters and even threaten the safety of the dam body. Therefore, when dealing with the harm of exceed-standard floods, new technologies and new ideas are urgently needed. On the premise of keeping the flood discharge capacity of the dam unchanged, through non-engineering measures of the reservoir, an emergency dispatching method is adopted to reduce the reservoir water level and the inflow and outflow at the same time, effectively reduce the flood peak, protect and give full play to the role of engineering measures, ensure the safety of the dam and downstream flood control targets, and reduce secondary and derivative disasters. Summary of the Invention

[0004] Aiming at the problem that the current conventional dispatching regulations adopted by reservoirs may fail when facing the threat of exceed-standard floods, the present invention provides a method for a reservoir to cope with exceed-standard floods by reasonably releasing the flood control storage capacity. By adjusting the non-engineering measures of the conventional dispatching regulations of the reservoir, more flood control storage capacity of the reservoir is released. Through the combination of flood discharge methods and the joint optimization of the starting and ending times of dispatching, the reasonable dynamic distribution of the flood control storage capacity of the reservoir can be realized, so that the reservoir can safely pass the flood season when facing floods with an inflow several times its flood control storage capacity.

[0005] The method for a reservoir to safely cope with the probable maximum flood by means of optimized dispatching provided by the present invention is as follows:

[0006] S1. According to the regulations of hydrological forecasting and reservoir operation rules, determine the flood hydrograph of the Probable Maximum Flood (PMF), that is, the flood discharge corresponding to different flood durations. The purpose of this step is to obtain the flood discharge of each time period during the coming process of the PMF. The flood process of the PMF can be obtained through hydrological forecasting or the results of the design flood volume calculation in each reservoir operation rule.

[0007] S2. Specify the opening and closing conditions of each flood discharge structure in the reservoir and the flood discharge project system, as well as the flood discharge of each flood discharge structure at different openings. It should be strictly in accordance with the operation and management methods of the flood discharge structures specified in each reservoir operation rule. When determining the flood discharge of each flood discharge structure, emphasis should be placed on ensuring the safety of the downstream river channel, coordinating the contradiction between sediment flushing and flood regulation, and paying attention to meeting the requirements of the operation task and the safe operation conditions of the flood discharge facilities.

[0008] Step S3. Specify the flood control requirements of the reservoir and the flood control protection objectives of the downstream, determine the boundary conditions including the water level in front of the reservoir dam, the flood discharge, and the range of water level changes, and establish the constraint conditions. It includes the following two sub-steps:

[0009] S31. Based on the reservoir operation rules, clarify the flood control requirements of the reservoir, collect the allowable range of the water level in front of the reservoir dam, clarify the requirements of the flood control protection objectives of the downstream of the reservoir, and determine the maximum flood discharge of the reservoir.

[0010] S32. The constraint conditions for the reservoir operation according to the safety of the reservoir dam and the requirements of the reservoir operation flow are as follows:

[0011]

[0012] In the formula, E s represents the water level in front of the dam, in m; its upper limit value and lower limit value are represented by E MAX and E MIN respectively; W s represents the flood discharge, and W MAX represents the maximum value of the flood discharge. Constraint condition (1) means that the water level in front of the dam E s should be between the lower limit value E MIN and the upper limit value E MAX . Constraint condition (2) means that the flood discharge W s shall not exceed the upper limit value of the flow W MAX to protect the flood passage safety of the river channel downstream of the reservoir area.

[0013] S4. Establish a one-dimensional hydrodynamic model of the reservoir; it includes the following steps:

[0014] S41. Obtain the relevant parameters of the reservoir; specifically, taking a river-type reservoir as an example, before modeling the reservoir, the characteristic water level values and relevant parameters of the reservoir should be obtained first. First, it should be clear that the modeling range of the reservoir area is from the front of the dam to the end of the reservoir, and the total length of the reservoir, the normal storage level of the reservoir, the check flood level, and the lowest drawdown level should be determined. At the same time, data such as topographic data and cross-section data of the reservoir in recent years should be collected.

[0015] S42. Establish a one-dimensional hydrodynamic model of the reservoir: Various parameters required for establishing the model can be obtained according to the above steps. Then, a one-dimensional hydrodynamic model of the river-type reservoir is established in HEC-RAS according to the Saint-Venant equations.

[0016] When establishing the one-dimensional hydrodynamic model of the reservoir, the specific method is as follows:

[0017] (1) Select a calculation method from steady flow and unsteady flow according to the calculation needs;

[0018] (2) Abstract different river reaches from the natural river distribution, find the confluence points of the main stream and tributaries, the inflow nodes and outflow nodes of different river reaches, and find the location of the dam. Then, draw the hydrodynamic network of the river where the reservoir is located according to the calculation needs;

[0019] (3) Input the natural topography of the reservoir area into the model, including topographic boundaries, river bottom slopes, etc. to complete the modeling;

[0020] (4) Input the model boundary conditions, including the upstream and downstream flow boundaries of the model, the water level-flow relationship boundary of the water discharge structure, the free boundary, etc.;

[0021] (5) Set the initial conditions for the unsteady flow calculation method, and set the water level and flow rate when the possible maximum flood enters the reservoir;

[0022] (6) Set the calculation time step and the total calculation time;

[0023] (7) Set the roughness of the topography;

[0024] (8) Set the calculation output file format, output content, and output content interval.

[0025] S5. Solve the one-dimensional hydrodynamic model under unsteady flow conditions, including the following steps:

[0026] S51. Check and calibrate the one-dimensional hydrodynamic model:

[0027] After the modeling is completed, according to the unsteady flow calculation method, set the initial incoming flow conditions and the initial water level in front of the dam, set the flow rates of each tributary respectively, and solve the one-dimensional hydrodynamic model under unsteady flow conditions after the modeling is completed. If the solution cannot be obtained, there is an error in the model, and it is necessary to return to check the problems existing in the model construction process step by step. After correction, continue to solve until the model can correctly output the hydraulic characteristics such as the reservoir water surface line, the water levels and flow rates of each section.

[0028] S52. Calibrate the section roughness of the one-dimensional hydrodynamic model using the characteristic water levels of the reservoir in known years and different incoming flow rates, and complete the parameter correction of the model. It includes the following sub-steps:

[0029] (1) Set the initial roughness and its change range for segmented main streams of the model;

[0030] (2) Input the hydrological data of the measured year, including the incoming flow rate, the water level of the section in front of the dam, the flow rates of sections at different cumulative distances from the section in front of the dam, and the water level of this section;

[0031] (3) Set the number of iterations and the iteration accuracy;

[0032] (4) Use the hydrodynamic model under unsteady flow conditions for calibration calculation to obtain the calibrated roughness;

[0033] (5) If the calibrated roughness reaches the upper limit or the lower limit, use the calibrated roughness as the initial roughness, modify the upper and lower limit ranges, and repeat steps (2)-(4) until the roughness is within the upper and lower limit ranges, and complete the roughness calibration.

[0034] S53. Set the same incoming flow rate and the outgoing flow rates under various combinations of water discharge structures, solve the one-dimensional hydrodynamic model under unsteady flow conditions, obtain the water surface line (water level in front of the dam) and the downstream discharge corresponding to different combinations, compare these two indicators, and obtain the emergency reservoir operation plan that meets the flood control objectives. Specific operations: First, set the outgoing flow rate as the result obtained from the combination of the opening and closing modes of each water discharge structure specified in the reservoir's normal operation regulations, and then output the water surface line of the reservoir when dealing with the possible maximum flood under the normal operation regulations; then set the outgoing flow rate as the result obtained under the emergency operation regulations, and then output the water surface line of the reservoir when dealing with the possible maximum flood under the optimized emergency operation regulations.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) By optimizing and adjusting the opening and closing modes of different water discharge structures in the current reservoir operation regulations, the present invention improves the utilization rate of the flood control storage capacity of the reservoir, is more conducive to the reservoir releasing flood discharge pressure, and enables the reservoir to not only ensure the safety of the dam itself when dealing with floods exceeding the standard, but also take into account the flood control safety of the downstream.

[0037] (2) The present invention takes into account various risk factors affecting the reservoir operation effect and flood control safety, and quantitatively discusses the impacts of main risk factors such as inflow flood discharge, combined opening and closing of flood discharge structures, and initial starting water level, etc., and can more truly reflect the operation effect of the reservoir under the influence of various risk factors when dealing with the possible maximum flood.

[0038] (3) When the reservoir is dealing with floods exceeding its own design standard, in addition to ensuring the safety of the dam itself, it should also fully pay attention to the flood control requirements downstream of the reservoir. For reservoirs with important flood control protection targets downstream, when dealing with over-standard floods such as PMF, the flood discharge volume can be increased and the flood discharge can be advanced earlier by adjusting and optimizing the opening and closing mode of flood discharge facilities. Taking the safety of the dam and downstream as the goal, an emergency operation method can be obtained to maximize the flood control and beneficial utilization benefits of the reservoir.

[0039] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0040] Figure 1 、Schematic flow chart of the method for the reservoir of the present invention to safely cope with the possible maximum flood through optimized operation.

[0041] Figure 2 、Flood process of the possible maximum flood in the embodiment provided by the present invention.

[0042] Figure 3 、Graph of the comparison process of the discharged flow rate and the water level in front of the dam during the optimization process in the embodiment provided by the present invention.

[0043] Figure 4 、Graph of the comparison of the water surface line changes before and after optimization in the embodiment provided by the present invention, where (a) is the water surface line before optimization and (b) is the water surface line after optimization.

[0044] Figure 5 、Graph of the comparison of the discharged flow rate and the water level in front of the dam before and after optimization in the embodiment provided by the present invention. Detailed Embodiment

[0045] The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0046] Taking a certain river-type semi-yearly regulating reservoir as an example, the process of the method for the river-type reservoir to cope with the possible maximum flood through optimized operation is described as follows, and the method process is as Figure 1 shown.

[0047] Step 1: Determine the possible maximum flood process:

[0048] After comparing various combination schemes and combination modes during the feasibility study stage of the reservoir, the possible maximum flood of the reservoir is composed of the possible maximum flood in the interval and the corresponding typical flood upstream. Since no larger storm floods have occurred in the neighboring areas, the results of the feasibility stage are still adopted in this embodiment, and the upstream boundary condition of the model is selected as the time-varying process of PMF flood within 72 hours, as Figure 2 shown.

[0049] Step 2: Specify the opening and closing methods and combination conditions of each flood discharge structure of the reservoir. The main flood discharge structures of the reservoir include the 1# and 2# flood discharge and sediment flushing tunnels, the sediment flushing and emptying tunnel, the spillway, and the water diversion and power generation system composed of 4 units. According to the current reservoir operation regulation, starting from the arrival of PMF at the reservoir area, all four units participate in flood discharge, the sediment flushing and emptying tunnel and the 1# flood discharge and sediment flushing tunnel are opened, and the opening degree is controlled so that the downstream discharge does not exceed the fixed maximum discharge of 2393 m 3 / s; when the reservoir water level exceeds the flood control high water level of 861.6 m, half of the units are closed, and the sediment flushing and emptying tunnel and the 1# flood discharge and sediment flushing tunnel are fully opened. At this time, the downstream discharge is not controlled to ensure the safety of the dam; when the reservoir water level exceeds 869 m, all units are closed, and when it exceeds 870 m, the spillway is opened for flood discharge.

[0050] Step 3: Construct the constraint conditions. According to the reservoir operation regulation, the maximum operating water level of the reservoir is the check flood level of 883.1 m. Therefore, to ensure the safety of the dam, when facing PMF, it should first be ensured that the water level in front of the reservoir dam does not exceed the check flood level. Secondly, when considering the flood carrying capacity of the downstream river channel of the reservoir, the downstream discharge of the reservoir and the flood in the downstream river channel should be superimposed at the same frequency, and the situation where the upstream flood of the reservoir and the peak value of the flood in the downstream river channel of the interval encounter at the same frequency is considered as the most unfavorable working condition. After calculation, the safety discharge of the reservoir is selected as 2393 m 3 / s. Therefore, to ensure the safety of downstream targets during flood discharge, the discharge of the reservoir should be as low as possible below its safety discharge.

[0051] Step 4: Establish a one-dimensional hydrodynamic model of the reservoir. Determine that the controlled drainage area above the dam site of the reservoir project is 22,662 km 2 , the average annual flow is 469 m 3 / s, the total annual runoff is 14.8 billion m 3 , the normal storage level of the reservoir is 877 m, the flood limit level is 850 m, the dead water level is 817 m, the flood control high water level is 861.60 m, the design flood level is 871.20 m, the check flood level is 883.10 m, the total reservoir capacity is 1.112 billion m 3 , the reservoir capacity below the normal water level is 0.998 billion m 3 , and the flood control reservoir capacity of the reservoir is 0.1664 billion m 3。Based on the one-dimensional hydrodynamic equation of the river channel, a one-dimensional hydrodynamic model of the reservoir is established: The one-dimensional hydrodynamic equation of the river channel is as follows:

[0052]

[0053]

[0054] In the formula: Z is the water level, m; Q is the flow rate, m 3 / s; A is the cross-sectional area of the flowing water, m 2 ; B is the water surface width, m; L q is the lateral inflow per unit river length, m 3 / s; g is the acceleration due to gravity, m / s 2 ; x is the distance along the river, m; S f is the hydraulic gradient.

[0055] Step 5: Before solving the model, first use the measured inflow, outflow, and meteorological boundary conditions of the reservoir in 2020 as the model input to calibrate the cross-sectional roughness of the one-dimensional hydrodynamic model, and then complete the parameter correction of the model. The correction of the specific roughness includes the following steps:

[0056] 1. Set the initial roughness and its variation range for each section of the main stream of the model.

[0057] 2. Input the hydrological data of the measured year, which should include the incoming flow rate, the water level at the section in front of the dam, the flow rates at different cumulative distance sections from the section in front of the dam, and the water level of this section.

[0058] 3. Set the number of iterations and the iteration accuracy.

[0059] 4. Use the hydrodynamic model under unsteady flow conditions for calibration calculation to obtain the calibrated roughness.

[0060] 5. If the calibrated roughness reaches the upper or lower limit, use the calibrated roughness as the initial roughness, modify the upper and lower limit ranges, and repeat steps 2 - 4 until the roughness is within the upper and lower limit ranges to complete the roughness calibration.

[0061] Perform calibration verification calculations on the model according to the above steps. After multiple calibration calculations, the value of the calibrated roughness is 0.035.

[0062] S53. After completing the calibration of the model parameters, by setting the same inflow and the outflow at various combinations of discharge structures, the one-dimensional hydrodynamic model under unsteady flow conditions can be solved to obtain the water surface profile and its downstream discharge corresponding to different combinations.

[0063] When the 2# flood discharge tunnel is opened at different water levels, the water level in front of the reservoir dam and the discharge flow rate will change. These data are respectively input into the model to obtain the water level in front of the dam and the discharge flow rate of the reservoir under different working conditions, as Figure 3 shown. Figure 3 (a) is the discharge flow rate diagram, and (b) is the water level diagram in front of the dam. Figure 3 The flow rate represented by the white slice in it is 2393 m 3 , which is the maximum discharge flow rate of the reservoir under the premise of ensuring the flood discharge safety of the downstream river channel. When it is exceeded, the downstream of the reservoir will face the risk of flood disasters. Generally speaking, opening the 2# flood discharge tunnel at different water levels has a significant impact on the change of the reservoir discharge flow rate. Specifically, when it is opened at a higher water level, the peak value of the reservoir discharge flow rate is lower and the change is relatively stable. At the same time, the duration of exceeding the maximum allowable discharge flow rate is shorter. It can be seen that the water level in front of the dam and the discharge flow rate have similar change laws: that is, when the 2# flood discharge tunnel is opened at a higher water level, the peak value of the water level in front of the dam is lower and relatively stable. And due to the increase in the discharge flow rate, the water level in front of the dam does not exceed 883.1 m under each working condition, ensuring the safety of the dam. At the same time, by comparing the change process of the reservoir discharge flow rate and the water level in front of the dam under the aforementioned current dispatching rules, it is not difficult to find that the optimized emergency dispatching rules can effectively improve the phenomenon that the reservoir discharge flow rate exceeds the maximum allowable flow rate downstream for a long time, and at the same time can keep the water level in front of the dam relatively stable, ensuring the safety of the dam and the downstream.

[0064] By comparing the change laws of the water level in front of the dam and the reservoir discharge flow rate, it can be found that when the 2# flood discharge tunnel is opened when the water level in front of the dam is at 864 m, the threat to the safety of the dam and the downstream river channel is the smallest. Therefore, the following optimizations are made to the current dispatching rules: when the PMF flood enters the reservoir, all units are opened for flood discharge, and at the same time, the 1# flood discharge tunnel and the scour prevention and air defense tunnel are fully opened for free discharge. The 2# flood discharge tunnel is opened at 864 m to participate in flood discharge, and all generating units are closed at 869 m as the emergency dispatching rules.

[0065] Compare the performance of the reservoir when discharging floods using the optimized rules and the original dispatching rules during the PMF. The comparison results are shown in Figure 4 、 Figure 5 and Table 1. It can be seen that when using the optimized rules for dispatching, the peak shaving rate of the reservoir is significantly higher than that of the original rules, increasing from 58% to 74%. The flood with the upstream maximum inflow rate of 12200 m 3 / s is safely discharged at the outflow rate of 3139.74 m 3 / s, effectively reducing the flood peak water level by about 23 m and minimizing the flood control pressure downstream of the reservoir.

[0066] Table 1 Comparison of dispatching results of two schemes

[0067]

[0068] In summary, through the combined mode of flood discharge methods and the joint optimization of the start and end times of scheduling, the present invention realizes the reasonable dynamic allocation of the flood control storage capacity of the reservoir, thereby providing a new method for the reservoir to carry out emergency scheduling in the face of exceeding-standard or extreme floods.

[0069] The above are only preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention by using the above-disclosed technical content. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for a reservoir to safely respond to the possible maximum flood through optimized scheduling, characterized in that, The steps are as follows: S1. According to the regulations of hydrological forecasting and reservoir operation rules, determine the flood process of the possible maximum flood, that is, the flood discharge corresponding to different flood durations; S2. Clarify the opening and closing conditions of each flood discharge structure in the reservoir and the flood discharge project system, as well as the flood discharge of each flood discharge structure at different openings; S3. Clarify the flood control requirements of the reservoir and the flood control protection objectives downstream, determine the boundary conditions including the water level in front of the reservoir dam, the flood discharge, and the range of water level changes, and establish constraint conditions; S4. Establish a one-dimensional hydrodynamic model of the reservoir; including the following steps: S41. Obtain the relevant parameters of the reservoir; S42. Establish a one-dimensional hydrodynamic model of the reservoir: First, select the calculation method from steady flow and unsteady flow according to the calculation needs; Second, abstract different river reaches from the natural river channel distribution, find the confluence points of the main stream and tributaries, the inflow nodes and outflow nodes of different river reaches, find the location of the dam, and then draw the hydrodynamic network of the river channel where the reservoir is located; Input the natural topography of the reservoir area river reach into the model to complete the modeling; S5. Solve the one-dimensional hydrodynamic model under unsteady flow conditions, including the following steps: S51. Check and calibrate the one-dimensional hydrodynamic model; S52. Use the characteristic water levels of the reservoir in known years and different incoming flow discharges to calibrate the cross-sectional roughness of the one-dimensional hydrodynamic model, and complete the parameter correction of the model; Specifically, it includes the following sub-steps: (1) Set the initial roughness and its change range for each section of the main stream of the model; (2) Input the hydrological data of the measured year, and the hydrological data includes the incoming flow discharge, the water level of the cross-section in front of the dam, the flow discharge and the water level of the cross-section at different cumulative distances from the cross-section in front of the dam; (3) Set the number of iterations and the iteration accuracy; (4) Use the hydrodynamic model under unsteady flow conditions for calibration calculation to obtain the calibrated roughness; (5) If the calibrated roughness reaches the upper limit or the lower limit, use the calibrated roughness as the initial roughness, modify the upper and lower limit ranges, and repeat steps (2)-(4) until the roughness is within the upper and lower limit ranges to complete the roughness calibration; S53. Set the outgoing flow under the same incoming flow and various combinations of flood discharge structures, solve the one-dimensional hydrodynamic model under unsteady flow conditions, obtain the water surface profile and its flood discharge corresponding to different combinations, compare the two indicators, and obtain the emergency reservoir operation plan that meets the flood control objectives.

2. The method for the reservoir to safely respond to the possible maximum flood through optimized scheduling as claimed in claim 1, wherein The said step S3 includes the following two sub-steps: S31. Based on the reservoir operation rules, clarify the flood control requirements of the reservoir, collect the allowable range of the water level in front of the reservoir dam, clarify the flood control protection objective requirements downstream of the reservoir, and determine the maximum flood discharge of the reservoir; S32. According to the requirements of the reservoir dam safety and the reservoir operation flow, the constraint conditions for the reservoir operation are as follows: In the formula, E s represents the water level in front of the dam, in m; its upper limit value and lower limit value are represented by E MAX and E MIN respectively; W s represents the discharge flow rate, and W MAX represents the maximum value of the discharge flow rate.

3. The method for the reservoir to safely respond to the possible maximum flood through optimized scheduling as claimed in claim 1, characterized in that, In the said step S41, obtaining the relevant parameters of the reservoir includes the total length of the reservoir, the normal storage water level of the reservoir, the check flood level, and the lowest drawdown level, and at the same time collect the topographic data and cross-sectional data of the reservoir in recent years.

4. The method for the reservoir to safely respond to the possible maximum flood through optimized operation as claimed in claim 3, characterized in that, In the step S42, initial conditions are set for the non-steady flow calculation method, including setting the water level and flow rate at the time of the possible maximum flood inflow, setting the calculation time step, calculating the total time, setting the terrain roughness coefficient, setting the calculation output file format, the output content, and the output content interval.

5. The method for the reservoir to safely respond to the possible maximum flood through optimized operation as claimed in claim 1, wherein In the step S51, if there is a situation where the solution cannot be obtained, it means there is an error in the model. It is necessary to return and gradually check the problems existing in the model construction process. After correction, continue the solution until the model can correctly output the hydraulic characteristics such as the reservoir water surface line, water levels and flow rates at each section.

6. The method for the reservoir to safely respond to the possible maximum flood through optimized operation as claimed in claim 1, characterized in that The step S53 is specifically as follows: First, set the outflow discharge as the result obtained from the combination of the opening and closing modes of each flood discharge structure specified in the reservoir's normal operation regulation, and then output the water surface line of the reservoir when coping with the possible maximum flood under the normal operation regulation. Then, set the outflow discharge as the result obtained under the emergency operation regulation, and then output the water surface line of the reservoir when coping with the possible maximum flood under the optimized emergency operation regulation.

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